This invention relates to an electrical switch that is sensitive to the location on its actuating surface where it is depressed by a user. The switch has particular application to a personal computer""s pointing device, commonly known as a mouse. A continuing problem with laptop computers is providing a compact, reliable and easy to use pointing device. The conventional mouse that fits in a user""s palm is not an acceptable pointing device in a laptop computer because a laptop is typically used where there is no convenient desk surface on which to manipulate a conventional mouse. A conventional mouse is also too large for storage in a laptop computer. As a result of these drawbacks, laptops have not been equipped with a conventional mouse but instead have had various switches, trackballs and/or miniature joysticks built into their keyboards for use as pointing devices. These have met with varying success but many users still find them unsatisfactory. Cost and reliability are other concerns with prior art laptop mice. The present invention provides an electrical switch that resolves these problems and makes an excellent mouse switch. However, the switch is not limited to a mouse application. It can used anywhere a directional indication is needed.
The present invention concerns an electrical switch of the type having a conductive armature movable into and out of contact with a set of electrodes. The electrodes may be arranged to have spaced pads with the armature moving into and out of shorting relation with these pads. Or the electrodes may form a resistive element of a potentiometer with the armature providing a take-off element. Other electrode arrangements are possible to provide a desired logic or output. In any case, the electrodes are arranged to provide a variable output dependent on where the armature contacts the electrodes.
The switch has a carrier sheet on which the electrodes are formed. A coupler layer lies adjacent the carrier. A spacer separates the coupler and carrier and defines a cavity in which a conductive armature is disposed. The coupler is a magnet and the armature is made of material that is affected by a magnet. An aperture in the coupler provides access to the armature. A user-supplied actuating force acting through the aperture tilts a first portion of the armature into contact with the electrodes while a second portion of the armature remains in contact with the coupler. Any part of the armature can be pressed into contact with the electrodes so a variable output is produced depending on where the user pressed the armature. The coupler magnet retracts the armature from the electrodes when the actuating force is removed.
An alternate form of the switch has a set of electrodes arranged in a series of segments on a substrate. A conductive armature is normally held spaced from the electrodes by a magnet. The armature can be depressed to contact one of the segments and a central common contact. The armature can also be rotated to align conductive bumps on its underside with a selected subset of the segments. A further variation has an armature with a plurality of local crowns extending through a spacer for actuation by a user. In another arrangement a membrane switch is incorporated into the substrate. Yet another embodiment employs a resilient post underneath the armature to provide flexibility between the armature and sub-strate.